Asset-condition monitoring system

ABSTRACT

An ultrasound sensing system for monitoring the condition or integrity of a structure, comprising (a) a plurality of ultrasound sensors, each sensor being configured to receive at least one first electrical signal, transmit an ultrasound signal in response to the first electrical signal, receive at least one reflected ultrasound signal, and transmit a second electrical signal in response to the reflected ultrasound signal, the first and second electrical signals being analog; (b) at least one digital sensor interface (DSI) to which at least a portion of the sensors are connectable, the DSI being configured to transmit the first electrical signal and receive the second electrical signal, and to generate an A-scan signal based on the first and second electrical signals for each sensor, the DSI having circuitry for transmitting a digital signal based directly or indirectly on at least the A-scan signal, the digital signal including an address corresponding to the at least one DSI; (c) a digital bus configured to receive the digital signal from the at least one DSI; (d) a user interface connected to the bus to receive the digital signal; and wherein, in one embodiment, the sensors are mounted semi-permanently on the structure and the DSI is also mounted semi-permanently on or adjacent to the structure being monitored.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/058,592, filed Oct. 1, 2014, and U.S. Provisional Application No.62/137,532, filed Mar. 24, 2015, the entire disclosures of which areincorporated herein by reference.

FIELD OF INVENTION

The invention relates generally to a system for ultrasonicallymonitoring the condition and integrity of pipes and/or other structuresor assets, such as those used in the oil and gas and power generationindustries.

BACKGROUND

Wall thickness and the presence of defects such as cracks are importantfactors in determining the fitness-for-service of structures such asabove and below ground pipes and tanks. When a pipe is in operation, itcan be subject to corrosion and/or erosion due to the content, flowand/or environmental conditions inside or outside of the pipe. Crackscan form and propagate due to the presence of manufacturing defects,creep, thermal cycling, fatigue and environmental conditions resultingin high temperature hydrogen attack (HTHA) stress corrosion cracking,etc. Corrosion and/or erosion results in the reduction in wallthickness, which can reach a point at which operating conditions becomesunsafe, considering that the pipe can be pressurized and may containhazardous or flammable materials. Likewise formation and propagation ofcracks can cause similar unsafe conditions. A failure may causecatastrophic consequences such as loss of life and environmental damagein addition to the loss of the use of the asset, and any correspondingcosts associated with repair, loss of capacity and revenue loss.

Ultrasonic non-destructive evaluation techniques are commonly used forevaluating the integrity of industrial components. In the case ofmeasuring wall thickness reduction due to erosion/corrosion, thetraditional process involves using a portable handheld instrument andultrasonic transducer (probe) to measure the wall thickness. Theinstrument excites the probe via an electrical pulse, and the probe, inturn, generates an ultrasonic pulse which is transmitted through thestructure. The probe also receives an echo of the ultrasonic pulse fromthe structure, and converts the pulse back into an electrical signal.The ultrasonic pulses that are transmitted into and received from astructure are used to determine the relative position of the surfaces(i.e. thickness) of the structure wall. More specifically, by knowingthe travel time of the ultrasonic pulse from the outer wall to the innerwall and back (ΔT) and acoustic velocity (V) of the ultrasonic pulsethrough the material of the structure (through calibration or justinitialization), a wall thickness (d) can be calculated—i.e. d=ΔT*V/2.In a similar fashion, ultrasound can be used to detect the presence ofdefects such as cracks in bulk material or in welds. Here, the gauge isset up to look for the presence of ultrasonic echoes returning from thedefect. The presence of an echo in a particular area of interest wouldindicate the presence of a flaw. There are many variants of these twobasic descriptions of ultrasonic thickness gauging and flaw detectionthat are known to skilled practitioners of ultrasonic nondestructiveevaluation. These approaches require an operator to manually position aprobe on the wall of the asset to take a reading. Not only does thisnecessitate the operator manually taking each reading, but also themeasurement location must be accessible, which can be challenging andcostly. For example buried pipelines require excavation to access,insulated pipe requires costly removal of the insulation, offshoreassets require helicopter or boat access, and elevated vessels mayrequire scaffolding or crane access. While the measurement is relativelysimple, the cost of access (scaffolding, excavation, insulation removal,etc) is often much higher than the cost of measurement. Moreover, theoperator may be subjected to hazardous conditions while taking thereadings.

Another problem with the traditional approach is that the data iscaptured on a proprietary device, making the distribution and furtherprocessing of the data inconvenient and potentially subject totranslation errors if the data is recorded manually. That is, once thedata is acquired by the handheld device, the device usually needs to beconnected to a computer running a proprietary software to download,analyze and report the data. Often times the software is only licensedto a single computer so multiple software licenses are required.Furthermore, the technology requirements for the software installationscan be challenging and maintenance can be problematic—e.g., computerreplacement, operating system upgrades, etc. Additionally, inspectionreports are then written and often shared with the operator or assetowner via emailed or paper reports, but not via cloud based data access.

Furthermore, to obtain trending data with thickness resolution of 0.001″or better requires that the transducer be placed in the same exactlocation for consistent readings at regular time intervals. This isdifficult and often impractical especially when the data-capture rateneeds to be frequent. Variations in operator and/or equipment tend toskew the quality and integrity of the measurement data.

One approach for avoiding some of the aforementioned problems is to useinstalled sensors/systems for asset-condition or -integrity measurement.The sensors are permanently or semi-permanently installed on the assetand can be covered with soil, insulation and/or can be wired to aconvenient place for easy user access. This also overcomes thelimitation in manual thickness measuring that it is never possible toplace the sensor in the same position for subsequent readings resultingin inherent measurement error Automated systems require no operator tobe in the vicinity of the asset and can stream data to a control room orto an operator's desk.

Current permanently- or semi-permanently installed systems tend tosuffer, however, from a number of shortcomings. For example, some of thesystems require point-to-point connections between the user interfaceand the sensors. This becomes problematic as the number of sensors on astructure increases, requiring bundles of wire to be run to theinterface. Additionally, conventional systems tend to requireproprietary user interfaces to receive signals from the sensors and toapply proprietary algorithms to convert these signals to usable data.Thus, the user is forced to interface or download information from theseproprietary controllers to a PC/tablet or other user device. Still otherconventional systems use wireless signals between the sensor and thecontroller. Again, these links tend to be proprietary and require aproprietary controller to receive and process the data from the sensors.Such systems are also inappropriate for underground use. Further,wireless transmissions tend to be slower and thus latency in the systemcan be an issue. Yet another problem of the conventional system isanalog signals between the sensors and the controller. As is known,analogs signals are more susceptible to corruption and degradation, andthus misinterpretation, especially as the distance between the sensorand the controller increases.

Therefore, Applicants recognize a need for a system that is modular andfacilitates non-proprietary transmission of digital signals usingoff-the-shelf user interfaces. The present invention fulfills this needamong others.

SUMMARY OF INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

Applicants recognize that the proprietary, analog user interface used inconventional ultrasonic wall thickness measuring systems is cumbersomeand inconvenient, and subject to corruption/attenuation and otherundesirable effects. To minimize these shortcomings, Applicantsrecognize that “pushing” the proprietary and analog circuitry as closeto the sensors as practical and using a digital bus to interconnect thesensors increases the integrity of the data obtained and impartsmodularity by enabling the use of conventional, off-the-shelf userinterfaces. In particular, Applicants propose a system comprising adigital bus interconnecting one or more digital sensor interfaces(DSIs), which are proximate to the analog sensors and contain thenecessary circuitry to convert the analog sensor signals to digitalsignals and transmit these digital signals on the digital bus. Bylocating the proprietary interface—i.e., the DSI—as close to the sensorsas practical, most of the cabling and signal transmission is digital andnon-proprietary, and thus can be readily integrated with off-the-shelfconsumer electronic devices such as tablets, smart phones, and laptopswithout the need for converting/downloading or otherwise manipulatingsignals.

Such a system provides for a number of important benefits. For example,in one embodiment, the system of the present invention uses a standarddigital, multi-drop communication link, such as RS485/Modbus, or CANbus,to connect the user interface with the DSIs which in turn are connectedto the sensors. The multi-drop bus allows a single multi-pair wire toaccess multiple sensor and sensor installations reducing cable cost andinstallation complexity. Furthermore, standard bus/protocol allows DSIand sensor installation to be easily connected to other plant equipmentsuch as DCS (distributed control system) or SCADA (supervisory controland data acquisition) system.

In one embodiment, the user interface (i.e. tablet or cell phone)comprises digital connectivity via wired means such as USB or wirelessmeans such as Wi-Fi or Cellular communications. This enables the data tobe pushed from the user interface via wired or wireless connections.Such connectivity facilitates cloud data storage which may be used as acollection point for the ultrasonic wall thickness data as well asrelated information about the installation. Examples of relatedinformation could be device information such as serial numbers, assetinformation, GPS coordinates, installation photographs, nominal wallthickness information, wall thickness limits, and 3D asset models. Theability to push data to the cloud also facilitates hosting the systemthrough the Web. A Web-hosted user interface may be used for datadisplay and analysis such that an asset operator can view and analyzeits data from any Web connected computer or handheld device. Cloudstorage access also provides enhanced visibility to data and can also beadvantageous for meeting archiving and reporting requirements. It canfurther offer the ability to trigger automated alarms when an alarmthreshold condition is met. Such alarms could be delivered via email ortext message for instance. An additional advantage of cloudstorage/computing is the potential for advanced data post processing andanalytics.

Additionally, because the DSI is near the sensors and thus can performcomputations on the analog sensor signals before they become distorted,the DSI may be configured to execute relatively complex signalprocessing to provide for a host of different outputs and monitoringoptions, including, for example, ultrasonic imaging techniques such asultrasonic phased array/delay and sum beam forming and full matrixcapture (FMC)/total focusing method [TFM].

The proposed DSI is a general purpose ultrasonic interface to a varietyof sensor types. Advantageously, the electrical design of the DSI allowsthe connection of the transmitter and receiver channels to separatetransmit and receive elements. These elements can be separatetransducers or can be individual elements within a single transducerhousing as may be present in a dual element transducer or in an arraytype of transducer. Dual element transducers are particularly suited tothickness measurement of corroded and/or rough surfaces. Arraytransducers are useable for electronic control of the beam and can beused with the FMC and TFM methods mentioned previously.

Accordingly, one aspect of the present invention is an ultrasonic systemincorporating a multi-drop digital bus having a standard protocol. Inone embodiment, the system comprises: (a) a plurality of ultrasoundsensors, each sensor being configured to receive a first electricalsignal, transmit an ultrasound signal in response to the firstelectrical signal, receive a reflected ultrasound signal, and transmit asecond electrical signal in response to the reflected ultrasound signal,the first and second electrical signals being analog; (b) at least onedigital sensor interface (DSI) to which at least a portion of thesensors are connectable, the DSI being configured to transmit the firstelectrical signal and receive the second electrical signal, and togenerate an A-scan signal based on the first and second electricalsignals for each sensor, the DSI having circuitry and software fortransmitting a digital signal based directly or indirectly on at leastthe A-scan signal, the digital signal including an address correspondingto the at least one DSI; (c) a digital bus configured to receive thedigital signal from the at least one DSI; and (d) a user interfaceconnected to the bus to receive the digital signal.

Another aspect of the invention is a DSI proximate the sensors for usein an ultrasound sensing system for monitoring the condition orintegrity of a structure. In one embodiment, the DSI comprising: (a)analog transmit and receive circuitry to which at least one or moresensors are operatively connectable, the analog transmit and receivecircuitry being configured to transmit a first electrical signal to eachof the sensors and to receive a second electrical signal from the eachof the sensors responsive to the first electrical signal; (b) an analogto digital converter to convert data related to the first and secondsignals to a digital signal; (c) a digital processor to calculate anA-scan signal based on the digital signal; and (d) a digital transceiverto transmit digitally an output signal based on the A-scan signal.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a perspective view of one embodiment of the ultrasonic wallthickness measurement system of the present invention.

FIG. 2 shows a schematic of the embodiment shown in FIG. 1.

FIGS. 3a-3d show various applications for the system of FIG. 1.

FIG. 4 shows a block diagram of one embodiment of a DSI unit of thesystem of present invention.

FIG. 5 shows different sensor configurations.

FIG. 6 shows a schematic of one embodiment of the interface box betweenthe user hand-held device and the DSI.

FIG. 7 shows a schematic of a traditional phased array generating asteered focused beam.

FIG. 8 shows a schematic of one embodiment of a multi-element sensorconfigured for full matrix capture.

FIG. 9 shows an example of a matrix of data generated using the sensorof FIG. 8.

FIG. 10 shows an example of a reconstruction grid based on the matrix ofdata of FIG. 9.

FIG. 11 shows a schematic of one embodiment of the dual probe multiplex.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a perspective view and schematic view of oneembodiment of the ultrasound sensing system 100, 200, respectively, ofthe present invention is shown. In this embodiment, the system 100, 200functions to determine wall thickness of a structure 101, and comprisesa plurality of ultrasound sensors 102, 202. Each sensor 102, 202 isconfigured to receive a first electrical signal, transmit an ultrasoundsignal in response to said first electrical signal, receive a reflectedultrasound signal, and transmit a second electrical signal in responseto said reflected ultrasound signal. The first and second electricalsignals are analog. The system 100, 200 also comprises at least onedigital sensor interface (DSI) 103, 203 to which at least a portion ofsaid sensors 102, 202 are connectable. The DSI is configured to transmitsaid first electrical signal and receive said second electrical signal,and to generate a time-voltage waveform commonly known as an A-scanbased on said first and second electrical signals for each sensor. TheDSI has circuitry for transmitting a digital signal based directly orindirectly on at least said A-scan signal. In one embodiment, thedigital signal includes an address corresponding to said at least oneDSI. The system 100, 200 also comprises a digital bus 104, 204configured to receive said digital signal from the DSI(s), and a userinterface 105, 205 connected to said bus to receive said digital signal.These components are described in greater detail below.

DSI

At the heart of the system 100, is the DSI 103, 203. The DSI functionsto interface with the sensors 102, 202 and generate a digital signalrelated to the physical characteristics of a particular structure 101,201, including, for example, wall thickness, anomalies/cracks, or evenan ultrasonic image. In one embodiment, the DSI interfaces with thesensors by transmitting and receiving the first and second electricalanalog signals, as described above, and generating an A-scan signal fromwhich the wall thickness of the structure can be derived. A-scan signalsare well known and relate generally to a data presentation by whichintelligence signals from an object location are displayed. As generallyapplied to pulse-echo ultrasonics, the horizontal and vertical sweepsare proportional to time or distance and amplitude or magnituderespectively. Thus the location and magnitude of acoustical interfaceare indicated as to depth below the sensor. It should be understood,however, that the A-scan signal may be presented in different formsafter processing within the DSI.

Additionally, the DSI functions to generate a digital signal for outputonto the digital bus 104, 204 that is based on the A-scan signal. Animportant aspect of the invention is that the DSI generates andtransmits the digital signal which is based on known, non-proprietaryprotocols allowing it to be transmitted on known, non-proprietarydigital buses as described below. The digital signal may be baseddirectly or indirectly on the A-scan signal. More specially, in oneembodiment, the A-scan signal is merely converted to a digital signal,which is then transmitted on the digital bus (described below in greaterdetail). Alternatively, the digital signal may be indirectly based onthe A-scan scan. That is, the A-scan signal may be converted tothickness data as described above, and then the thickness data may betransmitted as a digital signal over the bus. Whether the signal isdirectly related to the A-scan signal or indirectly related to theA-scan signal is not critical to the claimed invention provided that theoutput of the DSI is a digital signal comporting with known protocols.

As discussed below, a significant benefit of converting the analogsignal in close proximity to the sensors, and transmitting a responsivedigital signal along a digital bus is that the digital signal tends tobe less susceptible to distortion/degradation than an analog signal.This allows for a number of desirable features, including, for example,longer distances between the DSI and the user interface and multiple DSIdrops. Additionally, because the DSI is near the sensors and thus canperform computations on the analog sensor signals before they becomedistorted, the DSI may be configured to execute relatively complexsignal processing to provide for a host of different outputs andmonitoring options, including, for example, ultrasonic imagingtechniques such as ultrasonic phased array/delay and sum beam formingand full matrix capture (FMC)/total focusing method [TFM] which arediscussed in greater detail below.

In one embodiment, the DSI can be configured to store data related tothe inspection, including the ultrasonic parameters, such asinstrumentation gain, gate positions, and calibration data, as well ascontextual data such as GPS coordinates for the DSI and TMLs, assetinformation, tag numbers, etc. This data may accompany or be integratedwith the digital signal transmitted on the digital bus by the DSI,thereby providing the user with critical information related to thespecific DSIs, sensors and contextual information of the readingswithout user intervention.

In one embodiment, the DSI stores parameters related to the asset andother system information. For example, stored DSI parameters may includethe following: Company ID Number; Company Name; Company Address; PhoneNumber; Site/Division; Plant; Asset; Collection Point ID; CollectionPoint Description; Collection Point GPS Coordinate; Modbus Address; DSISerial Number, DSI Tag Number, DSI Firmware Version (Micro). DSIFirmware Version (FPGA); DSI GPS Coordinate; # of DSIs in chain; # ofProbes Attached; Result Packet Version; Baud Rate; and Parity & # ofStop Bits.

Additionally, the DSI may be configured to store data related to sensorparameters. (As discussed below, the sensors are not generallyintelligent devices and thus usually do not have the ability to storeparameters.) Data corresponding to these parameters Examples of sensorparameters stored in the DSI may include the following: Probe Model;Probe Type; Probe Location; Probe GPS Coordinates; Nominal MaterialThickness; Minimum Material Thickness; Material Velocity; and Number ofValid Setups. Parameters such as minimum material thickness can be usedto automatically determine alarm states once a measurement has beenperformed. Other parameters related to automated alarming arecontemplated to be stored in the DSI memory. The present invention alsocontemplates storing images of the sensors and/or their locations on theasset to provide the user with a visual indication of where on the assetthe sensor data pertains.

Additional parameters associated with the measurement may include thefollowing: DSI Temperature; Material Temperature; Status; CalculatedThickness; Data/Time Stamp; Last Measure Thickness; LMT Date/Time Stamp;Pulser Width; Gain; Mux Switch Settings/# of Averages; Ascan StartPosition; Gate 1 Start Position; Gate 1 Width; Gate 1 Threshold; Gate 1Mode; Gate 1 TOF; Gate 1 Amplitude; Gate 2 Start Position; Gate 2 Width;Gate 2 Threshold; Gate 2 Mode; Gate 2 TOF; Gate 2 Amplitude; Gate 3Start Position; Gate 3 Width; Gate 3 Threshold; Gate 3 Mode; Gate 3 TOF;and Gate 3 Amplitude.

This data may be collected in different ways. For example, some of thedata such as sensor data and DSI related data may be self-generated bythe DSI during its initialization. Alternatively, this data may beentered by the user or otherwise downloaded by the user. Data related tothe context of a particular reading may be obtained by the DSI at thetime of the reading. Still other techniques for obtaining and storingdata related to these parameters will be known to one of skill in theart in light of this disclosure.

Once theses parameters are stored, the results reported by the DSI areessentially standardized. Specifically, in one embodiment, the user isnot required to enter data regarding the particular sensors being usedor the context of the reading. That information is providedautomatically with the reading data according to the user's preference.The information ensures a uniform inspection without regard to operatorknowledge of the installation. Thus, the inspection results areconsistent and data integrity is ensured.

The DSI may also use self-diagnostic information to indicate the“health” and proper operation of the DSI. Although different approachesfor self-diagnoses are contemplated in this disclosure, one approachinvolves the DSI performing a self-check when powered up and/or whenprompted to acquire data from the sensors. Such self-checks are wellknown to those of skill in the art in light of this disclosure. Once thediagnostic information is obtained, it can be compared to storedparameters corresponding to a healthy system to determine if a problemexists. In one embodiment, if a problem with the DSI or associatedsensor is detected by the DSI, a message is transmitted on the digitalbus indicating the problem, at which point the DSI may awaitinstructions or take itself or a sensor off-line if the problem issevere enough.

The DSI may be configured to interface with any known sensor. Forexample, in one embodiment, the DSI is a dual-channel ultrasonic device,meaning that it has two independent, analog, transmit and receivechannels. These channels can be used independently, each with anultrasonic sensor individually or together with a dual elementultrasonic sensor. In one embodiment, the DSI acts as a single-channelultrasonic device, meaning that it can be configured to transmit andreceive on any channel. These channels can be used independently, eachchannel being connected to a single ultrasonic sensor, or multiplechannels being connected to a multi-element ultrasonic sensor, such asan array.

In one embodiment, each ultrasonic channel is multiplexed using an arrayof switches to increase the number of measurement points. For example,if each channel of the DSI is multiplexed to 16 outputs, then eachchannel can be connected to 16 ultrasonic sensors for a total of 16measurement points. Alternatively, the channels may be used in pairswith dual-element sensors for a total of 8 measurement points.

Referring to FIG. 4, a block diagram of the architecture 400 of aspecific embodiment of the DSI is considered in detail. The analog partof the electronics (transmitter/receiver and multiplexers are not shownin any detail and are simply shown as the UT Block 401. From the UTblock 401, the analog RF signal is converted to digital data by theanalog to digital converter (ADC 402), preprocessed in a fieldprogrammable gate array (FPGA 403) and fed into the microcontroller 404.Around the microcontroller are various peripheral components includingthe power supply 405, Real Time Clock 406, temperature sensor interface407, serial EEPROM memory 408, and communication ports 408, such as,RS485 and CAN transceivers 408 a, 408 b, respectively, for themulti-drop network, a wireless transceiver 409 and a USB port 410.

Referring to FIG. 11, one embodiment of the dual probe multiplexer 1100is shown. In this embodiment, dual element transducers are supported bythe multiplexer or circuit 1100. As shown, the circuit is configured toallow a pulser 1101 and receiver 1102 to be connected to separately toindividual transmit 1111 and receive elements 1112 of sensors 1103. Acommon control 1110 (microcontroller or similar) is used to ensure thesettings of each individual switch 1111 a, 1112 a are set such that theTX and RX elements in the probe are connected to the pulser and receiverchannels at the same time. One of the key elements is the use ofseparate switches for TX and RX channels. This separation allows formaximum electrical isolation between the TX and RX sides of the probe,thus reducing electrical crosstalk and thus maximizing measurementperformance.

Sensors

The sensors function to convert between electronic signals andultrasonic signals. (As used herein, the term “signal,” unless otherwiseindicated, may be electrical or ultrasonic, and may be in the form ofelectrical energy, sound pulse and other forms of electromagnetic orsound waves.) Such sensors are well known and are also referred to astransducers. Typically sensors comprise a piezoelectric material such aslead zirconate titanate (PZT).

In one embodiment, the system of the present invention is configured tointerface with most known or commercially-available ultrasonic sensor,thus avoiding the need for proprietary sensors and their inherentexpense and limited availability. For example, referring to FIG. 5, avariety of sensors is shown for determining wall thickness and detectingcracks. The single-element sensor 501 both transmits and receivesultrasonic signals from the same element 501 a. Such a sensor isrelatively inexpensive and allows one sensor to operate on just onechannel. In one embodiment, a single-element delay sensor 502 iscombined with a solid (delay line) 502 b such that the delay line isdisposed between the sensor element 502 a and the asset 550. The delayline functions to extend the travel time for an ultrasonic signal,thereby increasing the time between the transmit and receive function,which improves the near surface resolution and also measurement accuracyof single element sensors.

Another approach to improve measurement resolution is to use adual-element sensor 503, which transmits an ultrasonic signal from oneelement 503 a, and receives the reflected ultrasonic signal with asecond element 503 b. Although application needs may vary, generally adual-element sensor can be advantageous for measuring heavily corrodedsurfaces as the electrical separation between transmit and receivechannels allows for the use of increased signal amplification withoutthe deleterious effect of amplifier saturation and recovery due to thetransmission pulse.

To measure cracks, voids, welds, or other anomalies that are notparallel to the mounting surface 551 of the asset 550, but generallymore perpendicular to the mounting surface, an angle-beam longitudinalwave sensor shear wave sensor 504 may be used. In one embodiment, theangle-beam sensor 504 is configured with an angled spacer (wedge) 504 ato angle the sensor such that it refracts a signal into the asset thatis angled relative to the rear surface 552 of the asset. When the signalimpinges on the rear surface 552, it is reflected at the same angle(angle of refraction) and continues to propagate in the asset wall 550.As shown, if the signal encounters a crack 553 or similar anomaly, thesignal is reflected such that it reflects off of the rear wall back tothe sensor 504. Alternatively, an additional angle beam sensor 505 maybe configured to receive the signal from the transmitting transducer. Adefect in the path of the signal will block the transmission to thereceiver, indicating its presence. The single, delayed, dual element,angle-beam L and shear wave sensors are well known in the art. Examplesof commercially-available sensors are available from manufacturers suchas Olympus NDT, Imasonic, and Blatek.

In one embodiment, groups of sensors are arranged in arrays such as atwo dimensional array 105, 205 or a linear array 106, 206, and thearrays interfaced with DSIs as described below. In one embodiment, thearray of sensors is fixed semi-permanently to the asset, thusfacilitating a wall thickness measurement at the location of eachsensor. The sensor array may be implemented in various embodiments. Forexample, referring to FIG. 1, a medusa configuration 107 is shown inwhich the sensors consist of individual probes and are cabled to the DSIvia relatively short (<6 ft) cables 108. In another embodiment, thesensor array and DSI are implemented in the same physical package 109,110 as shown in FIG. 1. In this embodiment, the array elements can belarge and only operated individually or they can be small (<4wavelengths) and be used in groups to electronically manipulate theultrasonic beam, and is typically referred to as a phased array. Anadvantageous embodiment when using a phased array transducer using suchprocessing methods as TFM allows the simultaneous inspection for boththickness and flaw detection. In another embodiment, the array sensor isfabricated such that it is flexible and can conform to the curvedsurface of a pipe, pipe elbow or vessel.

As mentioned above in connection with the DSI, each sensor's uniquelocation, both relative to the other sensors in the array and theirabsolute location as installed on the industrial asset, can bepermanently encoded, via a unique serial number or GPS location into themonitoring system for accurate tracking of all future measurements.

In another embodiment, provisions for temperature measurement areincluded in the system with associated sensors such as thermocouples andthermistors, and associated circuitry and software within the DSI. Inone embodiment, there is at least one temperature measuring device perultrasonic probe. For example, the temperature monitoring devices may beattached to or embedded into the ultrasonic transducers. In anotherembodiment, one temperature measuring device is used per severalultrasonic sensors. Temperature measurements are taken adjacent in time(just before, during, or after) an ultrasonic measurement and are usedto adjust the ultrasonic measurement for changes in ultrasonic(acoustic) velocity due to temperature change. This is required to makemore accurate (precise) ultrasonic thickness measurements for example. Asoftware algorithm embedded in the thickness measurement (d=v/2*T) canautomatically correct “v” for its predicated change in acoustic velocityas a function of asset temperature changes. Sensors for temperaturemeasurement are well known and include, for example, resistancetemperature detector (RTDs) or thermocouple

Digital Bus

The digital bus functions to interconnect the various DSIs on a commonconduit with the user interface. Multiple DSIs may be connected to sucha network in a linear, multi-drop configuration with a single conductor,such as coaxial cable. In one embodiment, the digital bus comprises asingle cable that provides both power and digital communications to theDSIs. In an alternative configuration, the DSIs are interconnected by afour conductor cable, two conductors for communication and two forpower. Still other configurations of the digital bus will be apparent toone of skill in the art in light of this application.

The digital bus uses a network protocol that supports multi-dropcommunications is used such that a single wire (or twisted-pair) canaddress multiple DSIs. The digital bus may use either parallel or bitserial connections, and can be wired in either a multi-drop (electricalparallel) or star topology or connected by switched hubs in the DSIs, asin the case of USB. Because the digital bus provides for multiple drops,one-to-one connections between the user interface and the sensors areeliminated. Rather, a single conduit, such as a coax, can interconnectthe various DSIs and the user interface, thus simplifying installationand improving the integrity of the system.

The digital bus may be any known or later-developed digital busfacilitating multiple drops using standard protocols. In one embodiment,the digital bus is based on the TIA-485-A standard, also known asANSI/TIA/EIA-485, TIA/EIA-485, EIA-485 or RS-485, which is a standarddefining the electrical characteristics of drivers and receivers for usein balanced digital multipoint systems. The standard is published by theTelecommunications Industry Association/Electronic Industries Alliance(TIA/EIA), and is hereby incorporated by reference. In anotherembodiment, the digital bus is based on CAN Bus (controller areanetwork), which is a message-based protocol, designed specifically forautomotive applications but now also used in other areas such asaerospace, maritime, industrial automation and medical equipment. In yetother embodiments, the digital bus is Universal Serial Bus (USB),Ethernet, or Power over Ethernet (PoE). Still other digital buses willbe obvious to one of skill in the art in light of this disclosure.

User Interface

The user interface 105, 205 functions as an interface between the systemand a user and has a variety of different embodiments. Because thedigital bus is preferably (but not necessarily) a standard bus, in oneembodiment, the interface may comprise standard, off-the-shelfcomponents for facilitating a connection to the DSIs.

For example, in one embodiment, the user interface 105 is simply aconnector 111, 211 for interconnecting a user mobile computationaldevice 112, 212 (e.g., a tablet, laptop computer, or smart phone) to thesystem. In this way, the connector of the user interface functions toprovide a “tap” for the user to access the system. The access may be viaa standard wired or wireless connection. In such an embodiment, theuser's mobile device is used to connect periodically to the DSIs and toobtain data from the sensors.

In one embodiment, the user interface comprises an interface between thedigital bus and the user's mobile device. It should be understood thatembodiments of such a user interface may vary according to applicationand user needs. For example, referring to FIG. 6, in one embodiment, theinterface 600 has one or more of the following features: (1) a converter601 to convert the digital bus between formats—e.g. to convert betweenUSB (common short distance PC bus format) to RS-485 (common longdistance industrial bus format); (2) a battery 602 to power the DSIs(unless the user's mobile device (e.g., PC/tablet) has sufficientbattery capacity to power the DSIs); (3) intrinsically safe (IS)barriers 603 for the both the digital bus and power outputs to limitenergy to the DSIs if the DSIs are placed in a potentially explosiveatmosphere; and (4) a housing 604 which may be NEMA rated according tothe application. It should be understood that the interface 600 may alsocontain industry standard connectors for interfacing with the user'sdevice and with the digital bus.

In another embodiment, the user interface comprises apermanently-installed controller 302 (see FIG. 3a ) for communicatingwith the DSIs. The controller may be any know device adapted tointerface with the DSIs on the digital bus and to withstand theenvironment in which the structure is situated. In one embodiment, thecontroller is a commercially available, non-proprietary computationaldevice such as, a ruggedized tablet or laptop computer, or otherportable computer. In one embodiment, the controller or mobile device isconfigured with software for providing a graphical user interfaceenabling the user to configure and operate the DSIs as well as toprocess, store and display data. In another embodiment, the controlleris not a computational device, but rather is configured to transmit datato a computation system, e.g. a cloud-based system. In anotherembodiment, the controller is a computational device which also uploadsdata as described below.

It should be understood that the present invention contemplates varioususer interfaces and that other user interfaces not disclosed herein willbe obvious to those of skill in the art in light of this disclosure.

Upload Connection

As mentioned above, the controller or mobile device may be configured toupload data from the DSIs. Accordingly, in one embodiment, thepermanently-installed controller or mobile device is a “connected”device having a standard wired digital connection such as USB, or morepreferably, a wireless connection such as Wi-Fi, telemetry, or cellularcommunications. The latter configuration allows the controller tocollect the data and then push data to cloud storage for easy access byinspection personnel or asset owners. As used herein, the termcloud-based storage is a model of data storage where the digital data isstored in logical pools, the physical storage spans multiple servers(and often locations), and the physical environment is typically ownedand managed by a hosting company. Cloud storage services may be accessedthrough a co-located cloud compute service, a web service applicationprogramming interface (API) or by applications that utilize the API,such as cloud desktop storage, a cloud storage gateway or Web-basedcontent management systems. Thus, cloud-based storage for the ultrasonicmeasurements and related installation parameters enables the use ofweb-based data access from any fixed or mobile device having Internetconnectivity. In one embodiment, access through web connected devicesand a browser based interface bypasses the need for backend softwarethat must be locally loaded and managed.

In one embodiment, the controller or mobile device transmits the A-scansignal or similar signal in essentially “raw” form for cloud-basedcomputing. Cloud computing relies on sharing of resources to achieveeconomies of scale. Cloud computing focuses on maximizing theeffectiveness of the shared resources. With cloud computing, multipleusers can access a single server to retrieve and update their datawithout purchasing licenses for different applications. Thus, in thisembodiment, cloud computing performs the calculations on the A-scansignal to determine wall thickness or detect flaws including cracking.The calculations can be relatively simple such as measuring wallthickness or complex such as the generation of images using full matrixcapture and the total focusing method. Cloud computing enables thisparadigm as the power and computational requirements that wouldotherwise be required on the DSI would result in excessive cost andsystem complexity.

Because of the system's modularity and non-proprietary user interface,the process for converting the A-scan signal to thickness data can beperformed anywhere in the system (e.g., DSIs, controller, user device)or outside the system (e.g., in the Cloud). For example, the DSI can beconfigured to generate the thickness data from the A-scan signal, or,alternatively, the controller or mobile device can be configured to notonly receive data from the DSI but also analyze and display the wallthickness data. Alternatively, the calculation may be performed by acomputer outside of the system after the data is uploaded to the Cloudor other data store. Generally, determining when and where to calculatethe thickness data from the A-scan signal is a question of optimization.For example, it may be preferable to convert the A-scan signal tothickness data in the DSI to save on storage space because the A-scansignal data consumes more space than the thickness data. On the otherhand, converting this signal to thickness data tends to require moreprocessing power, thus, more energy needs to be provided to the DSIwhich may be problematic for remote, self-sustaining systems that relyon solar power or battery power. Generally, sophisticated calculationsor data analysis tends to be better suited for implementation in thecloud. In addition, a cloud based service is well suited to calculatingand communicating alarms derived from the inspection results throughmedia such as text messaging or email.

Power

Power may be provided to the system in different ways. For example, inone embodiment, power is provided by the mobile unit which isinterconnected to the system through the user interface. In anotherembodiment, the user interface comprises a battery for powering thesystem (see, e.g., FIG. 6 and associated text). In such an embodiment,it may be preferable to provide a means of recharging the battery. Forexample, the user interface may be connected to a solar panel 301 to usesolar power to maintain a charge in a battery as shown in FIG. 3a .Alternatively, power may be provided via wind power or other knownenergy harvesting approach. In yet another embodiment, power is suppliedto the system through permanent electrical connection. Such anembodiment may be preferable in situations in which the structure islocated near a power source such as in a refinery, power plant or oilplatform. Still other means of supplying the system with power will beobvious to one of skill in the art in light of this disclosure.

Operation

Although the system of FIG. 1 pertains to manual system for monitoringwall thickness of an underground pipe, it should be understood thatother embodiments are possible. For example, referring to FIG. 3a-d ,different applications of the system are shown. Specifically, in FIG. 3a, the system has a permanently-installed controller for wireless, realtime monitoring of a buried pipe. Such a system may include a solarpanel 301 as described above. In FIG. 3b , the system is implemented onoffshore oil platforms. As shown in FIG. 3c , the system may beimplemented in refinery, chemical or power plants. In FIG. 3d , anembodiment similar to that shown in FIG. 3c but for apermanently-installed controller. Furthermore, in FIG. 5, a shear wavesensor is shown for interrogating a certain portion of a weld/crackrather than for determining thickness. Still other applications of thepresent invention will be obvious to one of skill in light of thisdisclosure.

Furthermore, while the features described thus far have involved eachtransducer transmitting a single signal to evaluate the health of anasset (e.g., a thickness transducer measuring the part thickness beneaththe transducer or a shear wave transducer interrogating a certainportion of a weld), the system of the present invention is not limitedto these applications. In particular, because the DSI is near thesensors and thus can perform computations on the analog sensor signalsbefore they become distorted, the DSI may be configured to executerelatively complex signal processing to provide for a host of differentoutputs and monitoring options, including, for example, ultrasonicimaging techniques such as ultrasonic phased array/delay and sum beamforming and full matrix capture (FMC)/total focusing method [TFM]

Ultrasonic imaging techniques involve the generation of an ultrasonicimage based upon many sound beams impinging upon an area of interest inthe asset/structure. It is well known to those skilled in the art to useultrasonic imaging to inspect for and size defects in welds.Specifically, ultrasonic images are beneficial for a number of reasonsincluding, for example, the increased volume of the portion of the assetthat is interrogated and the additional information that can be gleanedthrough visual or automated interpretation of the image. From aninstalled monitoring perspective, the formation of weld images tomonitor crack growth is particularly advantageous.

Typically, a transducer is moved along the part using roboticmanipulation, with “shots” being taken at predetermined intervals. Theresulting A-scans are converted into images such as B-Scan and C-Scantypes, which are known to those skilled in the art. However, as appliedto installed sensors, the use of mechanical manipulation to move thesensor is impractical.

To generate an image using a transducer that is permanently positionedrequires the use of phased array techniques in which a transducer issubdivided into many small elements that are each addressedindependently from an electrical standpoint. Beam focusing and steeringcan then be accomplished by controlling the sequence of firing theelements through applied time delays to the ultrasonictransmissions/receptions, and summing the A-scans from all elementstogether. This method is known to those skilled in the art, and isgenerically referred to as ultrasonic phased array and “delay and sumbeam forming,” which is discussed, for example, in “DiagnosticUltrasound Imaging: Inside Out”, 2^(nd) edition, Thomas Szabo, AcademicPress; 2 edition (Dec. 26, 2013), hereby incorporated by reference.

Referring to FIG. 7, a schematic view 700 of delay and sum beam formingis shown. Specifically, by applying a time delay sequence to theultrasonic transmissions/receptions, a single-focused shaped beam 701can be formed using a conventional phased array of sensor 702. In thismanner, a beam can be steered through the volume of an object tofacilitate ultrasonic imaging.

While the proposed use of phased array does allow an ultrasonic image tobe made with a permanently installed transducer, it is still typicallyimpractical because the phased array technique requires many parallelsystem channels and onboard processing which requires excessive cost andpower. While it is conceivable that any phased array instrument could beused in a permanently installed fashion, the cost and battery life ofsuch a system makes such a system impractical—at this time. Furthermore,the equipment may not be suitable for installation in the hostileenvironments adjacent to a transducer location and thus may require longumbilical cables between the probe and instrumentation. This is a commonissue when performing phased array inspections inside of nuclear powerplant containment. The long umbilical cables severely degrade testperformance.

As mentioned above, the present invention is not faced with the problemof signal degradation over long cable length because the DSI isproximate to the permanently installed phased array sensors, and, thus,can perform the computations prior to the sensor signals becomingdistorted. Specifically, in one embodiment, the DSI is configured tosupport single transmit and receive channels, and to use a switch matrixto allow the connection of the transmitter and receiver to anycombination of system channels. For example, a DSI with a switch matrixsufficient to connect to 16 transducer elements can be arbitrarilyconfigured with, for instance, the TX channel connected to element 1 andthe RX channel connected to Channel 16. This allows the DSI tofacilitate the known techniques of full matrix capture (FMC) and totalfocusing method [TFM], which are described, for example, in C. Holmes,B. Drinkwater, and P. Wilcox, “Post-processing of the full matrix ofultrasonic transmit-receive array data for non-destructive evaluation,”NDT & E International, vol. 38, no. 8, pp. 701-711, December 2005,hereby incorporated by reference. In this approach, the DSI has only asingle transmit and receive channel, and, therefore, can be designed tobe very low power. Further, in one embodiment, the TFM operation isperformed in post processing on a PC therefore the DSI is only requiredto collect and transmit data placing no additional computational burdenon the DSI.

The concept of full matrix capture is described by FIG. 8. A transducer800 having N elements 801 is shown, where the transmitter (TX) isconnected to transducer element j and the receiver is connected totransducer element i. A waveform is collected for each combination ofi=1 to N and j=1 to N, creating a matrix of data 901 as shown in FIG. 9.Thus, for an N element transducer, N squared A-scans 902 are collected.These A-scans 902 are transmitted from the DSI to a data collectiondevice such as a tablet PC, industrial PC or to cloud storage asmentioned above.

The second process in the image formation is called the total focusingmethod (TFM) and, in one embodiment, is performed outside the DSI, forexample, on the data collection device, in the cloud or with the user'sPC. Specifically, in one embodiment, the steps of applying TFM comprise:(1) defining a computation zone 1001 within the asset/structure. (2)Within that computation zone, defining a reconstruction grid 1000 withdefined shape and spacing as shown in FIG. 10. For example, arectilinear grid with 1 mm×1 mm spacing. (3) At each grid point,computing a time delay for each combination of transmit and receiveelement, so for an N element array, N{circumflex over ( )}2 time delaysare defined. (4) The data point in each A-scan that corresponds to thecalculated time in step 3 is collected and summed. This process isrepeated for all points of the reconstruction grid. (5) Optionally, aprocess known as scan conversion can be applied to resample the datapoints from the reconstruction grid to an image grid, for instance tomatch screen resolution. (6) A pseudo-color image may then be created byapplying a map of colors based upon the amplitude of the data points inthe image grid (or reconstruction grid). (7) Pseudo-A scans can also begenerated by “slicing” the reconstructed data in a single dimension.Additional operations such as upsampling, gating, threshold detection,and zero crossing measurements can be applied to the A-scan as are knownto those skilled in the art. Therefore, in this way, the system of thepresent invention can be configured to provide ultrasonic images ofasset portions of interest rather than simple measurement data.

The system of the present invention can also be configured to providesophisticated trending information because of the accuracy in therepeatability of the measurements taken. As mentioned above, because thepresent invention employs permanently installed sensors and storescontextual data, it essentially eliminates variations in repeatedmeasurements. This facilitates sophisticated monitoring for trends. Thiscoupled with the ability of cloud-based data analysis to provideconstant and sophisticated analysis of the data obtained, leads to moreadvanced alarm logic. For example, in thickness gauging, basic alarmingmight include performing an action such as sending a text message to aninterested party when the thickness of a TML falls below a prescribedminimum. This would be described by the following logical expression:

if (t<tmin=true) send alarm

Basic alarms that are common might also include multiple levels ofalarming such as t<twarning to flag a TML that has reduced to a pointthat an operator might want to watch the point but that is not at anabsolute minimum value. Corrosion rates might also be alarmed such as aninstance where the rate is greater than 10 mils per year.

While these alarms are useful, there is additional capability to be hadthrough the inclusion of more logical expressions. This is accomplishedby adding the following operators to the software such as the following:Not, And, Or, Equivalent and NEquivalent. For example, an expressioncould be constructed as follows:

if (t<twarning).and.(rate>10) send alarm.

Many other expressions will be obvious to those of skill in the art inlight of this disclosure.

Having thus described a few particular embodiments of the invention,various alterations, modifications, and improvements will readily occurto those skilled in the art. Such alterations, modifications, andimprovements as are made obvious by this disclosure are intended to bepart of this description though not expressly stated herein, and areintended to be within the spirit and scope of the invention.Accordingly, the foregoing description is by way of example only, andnot limiting. The invention is limited only as defined in the followingclaims and equivalents thereto.

What is claimed is:
 1. (canceled)
 2. An ultrasound sensing system for monitoring the condition or integrity of a structure, comprising: at least one ultrasound sensor being mounted permanently or semi-permanently to said structure, said sensor being configured to transmit at least one sensor signal in response to at least one digital sensor interface (DSI) signal; and at least one DSI operatively connected to said sensor, said DSI being configured to transmit said DSI signal and receive said sensor signal, and to generate an A-scan signal based on said DSI and sensor signals for said sensor, said DSI being configured to calculate thickness data based on said A-scan signal and having circuitry for transmitting a digital signal comprising at least said thickness data and location data.
 3. The system of claim 2, wherein said location data is an address corresponding to said at least one DSI.
 4. The system of claim 2, wherein said sensor is physically connected to said DSI.
 5. The system of claim 4, wherein said sensor is cabled to said DSI.
 6. The system of claim 4, wherein said sensor is integrated physically with said DSI,
 7. The system of claim 2, wherein said sensor is wirelessly linked to said DSI.
 8. The system of claim 2, wherein at least some of said sensors are dual element sensors.
 9. The system of claim 2, wherein said at least one DSI is configured to periodically transmit said DSI signal, generate an A-scan signal, and store said thickness data, and to transmit said digital signal at a subsequent, predetermined time.
 10. The system of claim 2, wherein said at least one DSI is configured to transmit said DSI signal in response to a polling request signal from a controller connected digitally to said DSI.
 11. The system of claim 2, wherein said DSI contains circuitry and software to interface to temperature monitoring devices, where at least one temperature monitoring device is mounted on the object under test.
 12. The system of claim 2, wherein said digital signal is transmitted on a digital bus, wherein said digital bus is a multi-drop bus.
 13. The system of claim 12, wherein at least one DSI comprises multiple DSIs each connected to said digital bus.
 14. The system of claim 2, further comprising a permanently-installed wireless controller for transmitting a wireless signal based on said digital signal.
 15. The system of claim 14, wherein said wireless controller is solar powered.
 16. The system of claim 2, wherein at least one sensor comprises a multi-element sensor and said DSI is configured to execute full matrix capture on data obtained from said multi-element sensor.
 17. The system of claim 16, further comprising a computational device, discrete from said DSI, configured to use a total focusing method on said data of said full matrix capture to generate an ultrasonic image.
 18. The system of claim 17, wherein said computational device is configured to use a total focusing method on said data of said full matrix capture to determine the thickness of an asset.
 19. The system of claim 2, further comprising: a digital bus configured to receive said digital signal from said at least one DSI; and a user interface connected to said bus to receive said digital signal.
 20. The system of claim 2, wherein said DSI is configured to transmit said digital signal wirelessly.
 21. The system of claim 2, wherein said one or more sensors comprises a plurality of sensors and wherein said plurality of sensors is connected to a single DSI. 